High-efficiency metal-free organic-dye-sensitized solar cells with hierarchical ZnO photoelectrode

Abstract

Self-assembled ZnO secondary nanoparticles have been fabricated as an effective photoelectrode for dye-sensitized solar cells (DSCs). The hierarchical architecture, which manifested the significant lightscattering, can provide more photon harvesting. In addition, dye-molecule adsorption was sufficient due to enough internal surface area provided by the primary single nanocrystallites. Two indoline dyes, coded D149 and D205, were used as the sensitizers of ZnO DSCs with the optimal energy conversion efficiencies of 4.95% and 5.34%, respectively, under AM 1.5 full sunlight illumination (100 mW cm À2 ). The enhancement of the open-circuit photovoltage (V oc ) and the short-circuit photocurrent density (J sc ) for D205-sensitized ZnO DSCs was ascribed to the effective suppression of electron recombination by extending the alkyl chain on the terminal rhodanine moiety from ethyl to octyl. Further evidence is obtained from the electrochemical impedance spectroscopy (EIS) which exhibits a longer electron lifetime for D205-sensitized ZnO DSC in comparison with the D149-sensitized one.

Multidimensional ZnO Architecture for Dye‐Sensitized Solar Cells with High‐Efficiency up to 7.35%

“…[ 8 ] After drying at 60 °C in air overnight, the NAs were then mixed with ethyl cellulose and terpineol with a weight ratio of 1:0.2:1.5 to form a viscous ZnO paste. [ 23 ] The ZnO NA fi lm was sequentially fabricated by doctorblading the as-prepared ZnO paste on the FTO/glass substrate (2.3 mm thickness, 8 ohm sq −1 , GEAO, China), following a programmed heating of 350 °C for 1 h and then stepwise rising to 450 °C at 10 °C min −1 . [ 24,25 ] Preparation of ZnO NA/NS Photoanode Films : The ZnO NA/NS fi lm was prepared via suspending the above-synthesized NA fi lm upside-down in a sealed bottle containing an aqueous solution of zinc nitrate with certain concentration (0.10 M, 0.15 M and 0.20 M) and 16.7 wt% of urea at 90 °C for 2 h to form layered hydroxide zinc carbonate (Zn 4 CO 3 (OH) 6 ·H 2 O), which further transforms into ZnO NS in the following annealing step (300 °C) with loss of H 2 O and CO 2 .…”

New insight into the enhanced photocatalytic activity of N-, C- and S-doped ZnO photocatalysts

“…With a direct band gap and band edge positions both similar as that of TiO 2 , ZnO demonstrates 10-100 folds higher electron mobility than TiO 2 , and thus reduced electrical resistance and enhanced electron Page 3 of 31 A c c e p t e d M a n u s c r i p t 3 transfer efficiency [25]. Therefore, ZnO has been proven to be a competitive candidate for a wide range of photocatalytic and photoelectrochemical applications [26][27][28][29].…”

Hierarchically Assembled ZnO Nanocrystallites for High‐Efficiency Dye‐Sensitized Solar Cells

“…Such a layer acts as an efficient blocking layer for electron back reaction between the conducting glass at the anode and the electrolyte, [21] improving the functional properties of the cells. This is the main innovation with respect to the work of Cao and co-workers, [16] leading to unprecedented PCE up to 7.5 %, which is larger than ZnO nanoparticles (6.58 %), [20] hierarchically structured ZnO without a blocking layer (5.4 %), [16,18] and hierarchically arranged ZnO nanowires (2.63 %).[15] As a further benefit, our method is extremely fast (no more than 1.5 h for the complete processing of a photoanode, while typically 8 h [16] or 10 to 14 h [10] are required), enabling its technological implementation.The compact layer in contact with the conducting glass was deposited by a standard spray pyrolysis procedure starting from a methanol/water solution of zinc acetate dihydrate (see the Experimental Section). The main layer of ZnO aggregates (samples 1-4) was obtained from a mixture composed of an ethanolic suspension of ZnO commercial nanoparticles and a methanol/water solution of zinc acetate dihydrate.…”